This invention relates to sputtering apparatus, and more particularly a magnetron type sputtering apparatus suitable to use ferromagnetic material as a target.
In the sputtering apparatus of this type, negative voltage is impressed upon a target disposed at the cathode under a pressure of 10.sup.-1 to 10.sup.-5 Torr to emit electrons from the target and the electrons are caused to whirl about the target so as to ionize gas molecules. The resulting ions are caused to collide against the target surface to sputter the target material so as to form a metal film on a substrate. In such sputtering apparatus, for the purpose of increasing the productivity of the film by improving the deposition rate it has been proposed to use magnetic field having a component parallel to the target surface in front of the target. In most cases, magnetic pole pairs are disposed on the rear side of the target so as to utilize the magnetic field reaching the front surface of the target therethrough.
However, where the target is made of ferromagnetic material, the magnetic poles on the rear side of the target are difficult to have an influence on the front side. For this reason, for the purpose of utilizing ferromagnetic material for sputtering, various proposals have been made. According to one proposal the magnet poles are disposed in front of the target. With this construction, however, there is a porblem that the pole surface may be sputterred. So poles should be covered by a material having the same or similar composition as the target.
In the sputtering apparatus with its magnetic poles covered by the shield, not only the sputtering speed of ferromagnetic material can be improved to some extent but also sputtering of the magnetic poles themselve can be prevented. However, when the sputtering deposition rate is increased further the temperature of the magnetic poles rises, thus degrading the characteristic.